The human peripheral nervous system relies on large amounts of sensory feedback to modulate the neural drive to organs and limbs. A disruption or loss of sensory feedback, for example through injury or illness, results in inappropriate motor commands to different body systems and a subsequent loss of normal function.
Certain technologies exist for stimulating nerves after feedback has been lost or disrupted. For example, cuff stimulators have been implanted in humans to prevent foot drop for those with hemiplegia, restore grip functionality for those with paralyzed hands, and restore elective voidance in individuals with incontinence following spinal cord injury. However, no platform currently exists to enable human amputees to achieve intuitive control of advanced upper-limb prostheses.
Additionally, many implantable neural interface technologies for stimulating nerves lack feedback from sensory systems in order to improve their neural activity modulation. This can be because of the difficulty in recording the small electrical signals generated by nerve axons.
The ability to effectively record the electrical signals from sensory nerves could be used to appropriately modulate neural systems and move functional restoration towards pre-injury levels. One promising technology—microchannel electrode arrays—has emerged, which fares well in the body environment without causing neural damage, and also records nerve signals at high signal-to-noise ratios. In rodent models, for example, high signal-to-noise ratio recordings bladder and cutaneous afferents have been obtained using dissected portions of lumbar roots implanted in microchannel electrode arrays.
One drawback of the current microchannel arrays used in animal experiments, however, is that they require gluing a separate silicone cover plate to the top of the array to seal, and electrically isolate, nerve strands in different channels. This technique may result in incomplete compartmentalization of nerves within their channels because there may be gaps between the top surface of the array and the bottom surface of the installed cover plate. In turn, this increases the likelihood of unwanted cross-talk, or electrical coupling, between adjacent microchannels, which compromises the functionality of the device. Cross-talk reduces the devices ability to discriminate neural activity in one channel from that occurring in adjacent channels.
Another drawback with current technology is damage to neural tissue during surgery. For example, axonal damage and cell death can result from neural inflammation caused by surgical trauma during the implantation of nerves into microchannels or cuffs.
Cuff electrodes can be distinguished among neural interfaces as one of the few types of electrodes capable of establishing long-term electrical connectivity with peripheral nerves. They can be used to monitor neural activity in animals and to treat neurological impairment in humans.
A need exists for improved technology to aide in the modulation of nervous system functioning in subjects with compromised neural function, which reduces the detrimental effects of surgical trauma while improving long-term function of nerves.